Chism scored a career-high 30 points as No. 14 Tennessee limited Downey's scoring opportunities in a 79-53 rout of South Carolina on Saturday night.
Chism, who has averaged 14.1 points in SEC play, was 11 for 17 from the field, including two 3-pointers, and hit 6 of 8 free throws. His previous high of 27 points came against Auburn on March 14, 2009.
"When Chism is able to do things like that, inside and out, defend like he did and lead the team, he is a very difficult matchup," Volunteers coach Bruce Pearl said. "South Carolina did not have an answer for him."
The Vols (18-4, 6-2) did have an answer for Downey, who entered the game averaging 31.6 points per game in SEC play. The Gamecocks point guard struggled to get off screens and blocks and scored only nine points before halftime.
By then, Tennessee had a 30-16 lead and full control over a South Carolina team that was coming off a six-day break.
The Vols won their sixth straight over the Gamecocks (13-9, 4-4) and ninth in 11 meetings, wrapping up a busy week that included a narrow win over Florida on Sunday and another at LSU late Thursday.
This week presents their toughest road stretch of the season, with visits to Vanderbilt (No. 20 ESPN/USA Today, No. 18 AP) and Kentucky (No. 3 ESPN/USA Today, No. 4 AP) up next.
"We talked a lot about if we were going to continue to win, we were going to have to play better," Pearl said. "The defense has been a constant for us."
Both Tennessee and South Carolina started strong on defense but sloppy on offense. Bobby Maze helped spark the Vols with back-to-back fastbreak shots, including a pull-up 3-pointer from the wing.
Tennessee then took control with a 9-0 run capped by a Chism layup for a 27-12 lead with 3:05 left in the first half.
Chism felt the Gamecocks' defense against him loosen, and Pearl had his players go inside as much as possible. It paid off as the Vols scored 40 in the paint.
"It was the way they guarded," Chism said. "I had to adjust to it, and I adjusted to it pretty fast in this game."
An 8-0 run early in the second half increased the Vols' hold on the game, and a 3 by Scotty Hopson gave them a 42-20 lead just under four minutes into the second half.
Hopson and Bobby Maze each added 11 points for Tennessee and Kenny Hall pulled in 11 rebounds.
The Gamecocks, who are now 1-6 on the road this season, couldn't recover with 27.6 percent shooting.
"We were just outplayed," Downey said. "It seems like they were getting all of the loose balls off of rebounds and things like that. We were just outplayed."
Downey did manage to be more effective after halftime, reaching the paint to draw fouls and get to the line. He hit 13 of 14 shots from the line and finished with 26 points.
South Carolina entered the game leading the league with 9.2 steals per game but only came up with two against the Vols. The Gamecocks committed 11 turnovers, which led to 16 Tennessee points, and had only four assists.
South Carolina coach Darrin Horn told his players to remember how they felt about their play with Florida up next.
"We don't want to be in this situation," he said. "Losing is one thing, but doing it when you don't feel like you even give yourself a chance is very disappointing."